This is roughly the same number as someone who drunk the legal limit of alcohol.

According to boffins even being mildly dehydrated can make it more difficult to concentrate and can lead to mood swings.

It is the first study linking dehydration and driving ability, and has been published in the journal Physiology and Behaviour.

Professor Ron Maughan, who led the sport and exercise nutrition team which did study, put male drivers through a range of tests on a lab-based driving simulator over a period of two days.

Each driver was tested on one day when they were given 200ml of water every hour, and another day when they were given just 25ml – the equivalent of about five sips.

On average, the participants made 47 driving errors while normally hydrated.

That number rose to 101 when they were on the ‘dry’ day.

Prof Maughan told the Sunday Telegraph: ‘We all deplore drink driving, but we don’t usually think about the effects of other things that affect our driving skills, and one of those is not drinking and dehydration.

‘There is no question that driving while incapable through drink or drugs increases the risk of accidents, but our findings highlight an unrecognised danger and suggest that drivers should be encouraged to make sure they are properly hydrated.’